Mammalian spermatogenesis is a continuum involving transformation and proliferation of spermatogonia, meiosis, and differentiation of spermatids which culminates with a complex haploid spermatozoan capable of fertilization. Refinement of the techniques used to prepare a suspension of spermatogenic cells has enabled the separation by velocity sedimentation of pachytene spermatocytes, round spermatids and residual bodies of sufficient purity to be amenable to biochemical analyses. The principal objectives of the research program are orientated to examine three fundamental problems related to spermatogenesis; the synthesis and subsequent transition of basic chromosomal proteins, the characterization and diminution of non-histone chromosomal proteins, and gene transcription in meiotic pachytene spermatocytes and post- segregational spermiogenic cells. It is anticipated that a coordinated study on these problems will establish correlates between gene activity and the transition, or metabolism, of specific chromosomal proteins. It is proposed that isolated chromatin from different fractions of spermatogenic cells will be subjected to biochemical fractionation. Chromatin will be dissociated in the presence of high sodium chloride and urea, then allowed to reconstitute at low salt concentrations. Irreversibly dissociated non-histone chrosomal proteins will be recovered and the reconstituted chromatin pellet acid extracted to obtain histones. The reconstituted non-histone proteins will be either a) extracted with phenol to yield a fraction of phosphoproteins, or b) fractionated further using DNA affinity techniques. Protein fractions wll be examined by appropriate polyacrylamide gel electrophoresis. The metabolism of these proteins will be correlated with observations on the level of gene transcription during spermatogenesis.